fix(config): 优化 layout

- 新增 从环境变量解析目录结构

src/layout.rs

@@ -1,36 +1,67 @@
 use anyhow::{Context, Result, bail};
+use std::env;
 use std::path::{Path, PathBuf};
-
-pub struct ShimLayout {
-    pub root_dir: PathBuf,
+use tracing::debug;
+pub struct Layout {
+    pub base_dir: PathBuf,
     pub bin_dir: PathBuf,
     pub tools_dir: PathBuf,
+    pub lua_file: PathBuf,
 }
 
-impl ShimLayout {
+impl Layout {
+    /// 自动解析目录布局：
+    /// 1. 优先使用环境变量 RSHIM_HOME
+    /// 2. 兜底回退到当前垫片可执行文件所在目录推断 (exe -> bin -> root)
+    pub fn discover(current_exe: &Path) -> Result<Self> {
+        // 策略 1: 环境变量优先
+        if let Ok(home_val) = env::var("MIMIC_HOME") {
+            let trimmed = home_val.trim();
+            if !trimmed.is_empty() {
+                debug!(home = %trimmed, "检测到 MIMIC_HOME，采用环境变量配置");
+                return Self::from_base_dir(PathBuf::from(trimmed));
+            }
+        }
+
+        // 策略 2: 相对路径自动推断兜底
+        debug!("未配置 MIMIC_HOME，尝试从当前可执行文件路径推断根目录");
+        Self::from_executable(current_exe)
+    }
+
+    /// 基于确定的根目录构建完整布局
+    fn from_base_dir(base_dir: PathBuf) -> Result<Self> {
+        if !base_dir.is_dir() {
+            bail!("指定的根目录不存在或不是有效目录: [{}]", base_dir.display());
+        }
+
+        let bin_dir = base_dir.join("bin");
+        let tools_dir = base_dir.join("tools");
+        let lua_file = base_dir.join("mimic.lua");
+
+        Ok(Self {
+            base_dir,
+            bin_dir,
+            tools_dir,
+            lua_file,
+        })
+    }
+
     /// 从当前可执行文件解析 shim 安装目录布局
-    pub fn from_executable(exe_path: impl AsRef<Path>) -> Result<Self> {
-        let exe_path = exe_path.as_ref();
+    fn from_executable(exe_path: &Path) -> Result<Self> {
+        // let exe_path = exe_path.as_ref();
         let bin_dir = exe_path
             .parent()
             .with_context(|| format!("无法获取程序 [{}] 的父级 bin 目录", exe_path.display()))?
             .to_path_buf();
 
-        eprintln!("bin_dir目录 {}", bin_dir.display());
+        debug!("bin_dir目录 {}", bin_dir.display());
 
-        let root_dir = bin_dir
+        let base_dir = bin_dir
             .parent()
             .with_context(|| format!("无法获取 bin 目录 [{}] 的父级 root 目录", bin_dir.display()))?
             .to_path_buf();
-        eprintln!("root_dir 目录 {}", root_dir.display());
+        debug!("base_dir 目录 {}", base_dir.display());
 
-        let tools_dir = root_dir.join("tools");
-        eprintln!("tools_dir 目录 {}", tools_dir.display());
-
-        Ok(Self {
-            root_dir,
-            bin_dir,
-            tools_dir,
-        })
+        Self::from_base_dir(base_dir)
     }
 }